Epidermis, the constantly self-renewing outer layer of skin, consists of several layers of cells. The innermost basal cells are capable of cell division and give rise to the suprabasal layers. During the course of terminal differentiation skin cells anquire keratohyalin granules, become progressively smaller and flatter and finally anucleate and die forming a protective stratum corneum are keratins, a family of proteins found in intermediate filaments of all epithelial cells. Many keratinization disorders have a clear genetic background. These include ichthyoses, epidermolytic hyperkeratosis, psoriasis and many disease of hair. Certain inherited diseases which are known to have a primary defect in a specific enzyme or protein can be diagnoses in utero. Recent progress in molecular biology has been already very successful in both mapping some of these diseased loci on the hyman genome and providing methods for prenatal diagnosis. In the proposed experiments probes for detecting restriction fragment length polymorphisms associated with human keratin genes shall be developed. DNA clones coding for the human keratins will be isolated and characterized. A small sample of individual human DNAs shall be screened for presence of restriction fragment length polymorphisms using keratin clones. finally, the possibility that keratin genes associated polymorphisms are in linkage with inborn disorders of keratinization shall be investigated in order to develop reliable in utero diagnostic tools for inherited disorders of keratinization. The above studies will be complemented by a computer-based analysis of homologies among intermediate filament gene and protein sequences. Evolutionary trees will be generated by "Phylogeny Analysis Using Parsimony" programs. DNA hybridization between human and simian genomes will also be analyzed. Finally, we shall introduce genetically engineered DNA constructs containing the human 65Kd keratin gene into mammalian cells.